El desarrollo de mente mediada. La instrucción en el desarrollo simbólico y conceptual Peralta, Olga Alicia; Salsa, Analía Marcela; Maita, María del Rosario; Taverna Loza, Andrea Sabina Este capítulo pretende ilustrar el rol de la mediación en el desarrollo de la mente. Las contribuciones que aquí presentamos examinan formas en las que la instrucción, concebida como un proceso de mediación ejerce una poderosa influencia sobre las capacidades cognitivas que los niños desarrollan. El concepto de mente mediada (Nelson, 1996; Tomasello, 2000) es investigado estudiando la instrucción en el desarrollo simbólico y en el desarrollo conceptual. Consideramos que entre los 2 años y medio y los 3, los niños disponen de un importante repertorio simbólico y conceptual de nivel básico. Nuestra hipótesis principal es que a partir de allí el conocimiento que depende de relaciones más abstractas y profundas se halla en proceso de formación por lo que este período puede ser especialmente sensible a la instrucción. Se presentan una serie de investigaciones microgenéticas con una metodología cuasi experimental cuyo propósito consistió en estudiar si la instrucción puede facilitar y promover el establecimiento de relaciones simbólicas y conceptuales de orden superior, en particular en cuanto a la comprensión de la función simbólica de un objeto y a la formación de categorías conceptuales. Consideramos que estas investigaciones ilustran el desarrollo de la mente mediada y tienen un potencial considerable de contribuir tanto al conocimiento de las habilidades y limitaciones cognitivas de los niños pequeños como al estudio de las relaciones entre aprendizaje y desarrollo.

Factores psicosociales asociados a la presencia de síntomas depresivos en el posparto inmediato Paolini, Cynthia Inés Introducción: La depresión posparto se refiere a un episodio depresivo, no-psicótico que tiene comienzo dentro de las 4 semanas después del parto y tienen consecuencias devastadoras para la salud de la madre, el bebé y el resto de la familia. La presencia de síntomas depresivos en el posparto inmediato constituye un factor de riesgo para el posterior desencadenamiento de una depresión posparto. Los conocimientos actuales indican que del 50 al 70% de las mujeres puérperas presentan Síntomas Depresivos en el posparto inmediato, y del 10 al 15% desarrolla una depresión posparto. Sin embargo, la mayoría de las investigaciones en el tema provienen de países desarrollados de cultura occidental y aún es desconocido el modo en que difiere la frecuencia y los factores asociados entre las diferentes culturas y países. La importancia de conocer las características de las mujeres que presentan síntomas depresivos en el posparto inmediato, en nuestra población, constituye un primer paso para la posterior detección precoz de aquellas mujeres susceptibles de desarrollar una depresión posparto. Objetivos: Detectar los factores psicosociales asociados a la presencia de síntomas depresivos en mujeres puérperas durante el posparto inmediato. Resultados: Desde junio a septiembre de 2008, un total de 20 mujeres puérperas, asistidas en dos hospitales públicos de la Provincia de Buenos Aires, fueron entrevistadas dentro de los 5 días después del parto. La frecuencia observada de síntomas depresivos, fue del 40% (8/20). Las variables significativamente asociadas fueron: tener otros hijos, haberse sentido físicamente mal durante el embarazo; red familiar débil; angustia y ansiedad durante el embarazo, mayor presencia de life events. Conclusiones: La relevancia de los factores psicosociales asociados la presencia de síntomas depresivos en el período posparto, nos lleva a reflexionar a cerca de la necesidad de la realización de estudios en el tema, en nuestra población, cuyas características difieren considerablemente de las de los países desarrollados de donde provienen la mayoría de las investigaciones realizadas.

La vulnerabilidad social y la gestión del riesgo. La ambivalencia y los temores en la gestión del riesgo Rojas, Maria del Carmen Desde que el tema de vulnerabilidad social entró en la escena de la discusión y debate, han crecido también de forma colateral, como era de esperarse, los argumentos de las relaciones entre vulnerabilidad como estrategia y acción y gestión del riesgo como practica distinta, pero complementaria. Nadie podría negar que los dos temas tengan mucho en común y, a la vez, si se es realista y crítico, muchas cosas distintas. Hay un creciente número de organizaciones e individuos que han escrito sobre estas diferencias y similitudes. A la vez pareciera que existe un vacío de conocimiento, una transposición de ideas y una confusión creciente que a la vez une y desune. Hay otro aspecto digno de mencionar, los adeptos a Gestión De Riesgo (GDR) rara vez profundizan en la literatura sobre Vulnerabilidad Social (VS), y lo mismo al revés. Asimismo, se vive en una época donde se experimentan estados de ansiedad constante por los peligros que azotan sin previo aviso y en cualquier momento como los desastres naturales, las catástrofes medioambientales,  entre otras tantas cuestiones. Muchas transformaciones se suceden y  afectan por igual a las estructuras estatales, las condiciones laborales, las relaciones interestatales, la subjetividad colectiva, la producción cultural, la esfera íntima de las relaciones amorosas y la amistad, la vida cotidiana, y las relaciones entre el ser y el (los) otro (s). Las amenazas se tornan difusas, dispersas, poco claras y provocan miedo. Según Bauman[1] (2007) el miedo es el nombre que se da a la incertidumbre, a la ignorancia con respecto a la amenaza y a lo que hay que hacer –a lo que puede hacerse y no puede hacerse- para detenerla en seco o para combatirla, si pararla es algo que ya no esta al alcance. A todo esto se suma la ambivalencia de la identidad que resulta de la nostalgia del pasado y conformidad absoluta con el ethos de la modernidad líquida; padece el trance de querer al mismo tiempo las seguridades de un tiempo pasado, evaporadas por el resquebrajamiento de las estructuras que sostenían los vínculos de la modernidad sólida  y las libertades emanadas justamente de esa ausencia de vínculos en un tiempo presente vaporoso e inasible (Bauman, 2003). Ante este contexto se instalan las nociones de VS y GDR. Entonces, cabe la pregunta ¿podrán los conceptos sobre la ambivalencia y el miedo aclarar la confusión que une y desune en el análisis VS y GDR? [1] Zigmunt Bauman es profesor emérito de la Universidad de Leeds. Su producción data de los años 50 y se ocupa entre otros temas de cuestiones como clase, socialismo, hermenéutica, modernidad y postmodernidad y globalización entre otros.

Addenbrooke's Cognitive Examination validation in Parkinson's disease Reyes, M. A.; Perez Lloret, Santiago; Gerscovich, E. R.; Martin, M. E.; Leiguarda, R.; Merello, Marcelo Jorge Background: There is a clear need for brief, sensitive and specific cognitive screening instruments in Parkinson's disease (PD). Objectives: To study Addenbrooke's Cognitive Examination (ACE) validity for cognitive assessment of PD patient's using the Mattis Dementia Rating Scale (MDRS) as reference method. A specific scale for cognitive evaluation in PD, in this instance the Scales for Outcomes of Parkinson's disease - Cognition (SCOPA-COG), as well as a general use scale the Mini-mental state examination (MMSE) were also studied for further correlation. Methods: Forty-four PD patients were studied, of these 27 were males (61%), with a mean (SD) age of 69.5 (11.8) years, mean (SD) disease duration of 7.6 (6.4) years (range 1-25), mean (SD) total Unified Parkinson's Disease Rating Scale (UPDRS) score 37 (24) points, UPDRS III 16.5 (11.3) points. MDRS, ACE and SCOPA-COG scales were administered in random order. All patients remained in on-state during the study. Results: Addenbrooke's Cognitive Examination correlated with SCOPA-COG (r = 0.93, P < 0.0001), and MDRS (r = 0.91 P < 0.0001) and also with MMSE (r = 0.84, P < 0.001). Area under the receiver-operating curve, taking MDRS as the reference test, was 0.97 [95% confidence interval (CI): 0.92-1.00] for ACE, 0.92 (95% CI: 0.83-1.00) for SCOPA-COG and 0.91 (95% CI: 0.83-1.00) for MMSE. Best cut-off value for ACE was 83 points [Sensitivity (Se) = 92%; Specificity (Sp) = 91%; Kappa concordance (K) = 0.79], 20 points for the SCOPA-COG (Se = 92%; Sp = 87%; K = 0.74) and 26 points for MMSE (Se = 61%; Sp = 100%; K = 0.69). Conclusion: Addenbrooke's Cognitive Examination appears to be a valid tool for dementia evaluation in PD, with a cut-off point which should probably be set at 83 points, displaying good correlation with both the scale specifically designed for cognitive deficits in PD namely SCOPA-COG, as well as with less specific tests such as MMSE.

El proceso de descentralización de la educación en Argentina. Un caso: La provincia de Buenos Aires Formichella, Maria Marta; Rojas, Mara Carolina En el contexto de las transformaciones ocurridas durante las décadas `80 - `90 en América Latina, cabe destacar lo sucedido en el ámbito de la educación pública. En este trabajo se analiza el proceso de descentralización educativa llevado a cabo en la República Argentina, haciendo hincapié en el caso de la Provincia de Buenos Aires.

Reyes's syndrome, encephalopathy, hyperammonemia and acetyl salicylic acid ingestion in a city hospital of Buenos Aires, Argentina Lemberg, Abraham; Fernández, María A.; Coll, Carlos; Rosello, Diego O.; Romay, Salvador; Perazzo, Juan C.; Filinger, Ester Julia Twelve cases of Reye's syndrome are presented with different degrees of encephalopathy, hyperammonemia and hypoglycemia; associated to acetyl salicylic acid (ASA) ingestion. The aim of the present retrospective study was to describe our experience in selected patients with Reye's syndrome associated to the ASA ingestion and to underline the influence of hyperammonemia on Reye's encephalopathy. All the cases presented moderate hyperbilirubinemia, elevated alanine aminotransferase, aspartate aminotransferase with an average of 302±205 UI/L and 285±149 UI/L respectively. Arterial blood ammonia averaged 172.4±71.3 μmol/L and glycaemia averaged 35.2±17.0 mg/ dl. A high mortality was found in our series (41.7%). Considering that encephalopathy is the leading syndrome in these cases, the influence of ammonia on brain tissue was described. Glutamate is an excitotoxic neurotransmitter, capable to produce neuron and astrocyte damage and apoptosis. The presence of ASA could cause the onset of the mitochondrial permeability transition and the mitochondrial swelling in the astrocyte, leading to hyperammonemia. In Reye's syndrome, hyperammonemia and perhaps the increase of glutamate are the leading factors in the mechanism of brain damage and encephalopathy. Aspirin must be carefully administrated and controlled by professionals. Furthermore, parents must be informed about the risks in the use of this drug in children.

Análisis de la coherencia en los textos producidos en clases de Física en el nivel polimodal Domínguez, María Alejandra El trabajo que se comunica forma parte de una investigación más amplia que se centra en el estudio de la negociación de significados en clases de Física, tomando como indicadores los discursos argumentativos que se construyen en ese ámbito. La semiótica es una herramienta que permite analizar, a través de signos, la significación de todo lo que nos rodea. En particular, el estudio de la coherencia es uno de los indicadores para identificar modos de comunicación; no sólo interesa la coherencia manifiesta en el texto, sino también la que es recuperable mediante inferencias. Dado que la coherencia es la organización mínima del texto que permite acceder a otras interpretaciones, se supone que los alumnos deben ser capaces de elaborar discursos argumentativos coherentes para que el docente pueda tener éxito al interpretar el significado de los mismos. Se aspira a indagar si los alumnos son capaces de distinguir la organización global del texto base y elaborar un texto (resumen) que dé cuenta de las macroestructuras pertinentes. Es decir, derivar, por medio de las macrorreglas, proposiciones más generales. Los alumnos que no conseguieran recortar la información que no resulta prescindible, dejarían la incertidumbre en cuanto a si se ha podido captar la estructura global del texto; no se evidencia la utilización de las reglas de construcción y generalización y se encuentran ciertas incoherencias a lo largo de las producciones que se manifiestan en un incorrecto manejo de los mecanismos que operan en la estructura lineal. Se podría pensar en la posibilidad de trabajar la utilización de las reglas y la actividad de resumir, encontrar la estructura global de un texto y expresarla en un nuevo texto coherente.

¿Puede aprenderse química orgánica en la universidad presenciando una clase expositiva?; Can students learn organic chemistry in university being present at a lecture? Lorenzo, Maria Gabriela; Salerno, Alejandra; Blanco, María de Las Mercedes A study about the effect of the teacher´s lectures on students’ possibilities for solving some exercises of organic chemistry is presented. An investigation in context to 455 freshmen students with pencil-and-paper tasks of different complexity and different requirements was performed. The experimental design included the following independent variables: Condition of answering (previous, short-time, long-time), type of question (declarative concept, relational concept, technical and strategical procedure) and chemical contents (conformational analyses, nuclear magnetic resonance). The data were analyzed qualitatively and quantitatively. The responses were classified like correct (from the chemical point of view), incorrect (incomplete, regular, wrong) and not answered. Our results demonstrate that teacher participation is irreplaceable to promote student learning. This effect is not only visible in an increase of correct answers, but on the increase of total responses. Lectures affects principally on the using of technical language, the respect of conventions of chemical notations and on procedures for solving tasks.

New Fluorinated Pyrazol and Uracil Derivatives: Synthesis and Biological Activity Fustero, Santos; Sanz-Cervera, Juan F.; Simón-Fuentes, Antonio; Román, Raquel; Catalán, Silvia; Murguia, Marcelo Cesar Both fluorinated pyrazoles and uracils are compounds that display very interesting biological activity. This chapter reviews recent work or our group in the development of synthetic strategies for the preparation of new examples of these two kinds compounds.

Miedo, (in)seguridad y violencia en el entramado social Capdevielle, Julieta María Desde hace algunos  años el concepto de (in)seguridad cobra relevancia en las agendas mediáticas, y se convierte en una de las preocupaciones más importantes de la población.  Los lugares de enunciación vinculados a las "seguridad" operan, hoy por hoy, como una eficiente maquinaria de producción de visibilidad, credibilidad y, lo fundamental, agenda para el debate. Es así que, las encuestas revelan que, en la actualidad, la primera demanda de las poblaciones de Argentina, México, Brasil, Venezuela y Colombia es, precisamente, la de seguridad cotidiana. En Argentina, específicamente, la triada violencia, seguridad e inseguridad se reactualiza y cobra nuevos sentidos no sólo en los medios masivos de comunicación sino también por la demanda concreta de seguridad a través de prácticas y discursos de un sector de la sociedad.  A lo largo del presente trabajo buscamos analizar cómo ese discurso dominante sobre la inseguridad se filtra en el entramado simbólico de la sociedad y se transforma sedimentándose como sentido común. En esta reflexión nos  interrogamos no sólo por el sentido que se le otorga al concepto de seguridad, sino también por las prácticas concretas que conlleva o produce pensar en términos de esa seguridad. 

Dysregulation of stromal derived factor 1/CXCR4 axis in the megakaryocytic lineage in essential thrombocythemia Salim, Juan Pablo; Goette, Nora Paula; Lev, Paola Roxana; Chazarreta, Carlos Daniel; Heller, Paula Graciela; Alvarez, Clarisa Ester; Molinas, Felisa Concepción; Marta, Rosana Fernanda This study investigated the involvement of chemokines including stromal derived factor 1 (SDF-1), interleukin 8 (IL-8), growth-related oncogene alpha (GRO-a) and their receptors, CXCR4, CXCR2 and CXCR1 in essential thrombocythemia (ET), a chronic myeloproliferative disease characterized by megakaryocytic hyperplasia and high platelet count. Fifty-three ET patients were studied. Plasma levels of SDF-1, IL-8 and GRO-a, evaluated by enzymelinked immunosorbent assay, and flow cytometric analysis of CXCR1 and CXCR2 on the platelet membrane, were found to be normal in ET patients. CXCR4 expression on platelet surface aswell as platelet CXCR4mRNAdetected by real-time reverse transcription polymerase chain reaction, were decreased. Platelet CXCR4 internalization rate was normal while SDF-1-induced platelet aggregation was delayed, decreased or absent. Immunohistochemical staining revealed that megakaryocytes were also affected. CXCR4 decrease was not observed either in peripheral white blood cells or in circulating CD34+ precursors. These results show that CXCR4 is decreased in the megakaryocytic lineage in ET, mainly due to a reduced CXCR4 production, and an abnormal platelet response to SDF-1. This report is the first to describe platelet and megakaryocytic CXCR4 deficiency in a human disease and the presence of this abnormality in a megakaryocytic-related illness highlights the important role of SDF-1/CXCR4 axis in platelet development.

Detection of unintended stress effects based on a metabonomic study in tomato fruits after treatment with carbofuran pesticide. Capabilities of MCR-ALS applied to LC-MS three-way data arrays Sánchez Pérez, I.; Culzoni, Maria Julia; Siano, Gabriel German; Gil García, Magdalena; Goicoechea, Hector Casimiro; Martínez Galera, M. A chemometric strategy based on multivariate curve resolution and alternating least-squares (MCR-ALS) applied to LC-MS three-way data arrays has been developed to perform a metabonomic study in tomato (Lycopersicon esculentum) fruits (cultivar Rambo) following treatment with carbofuran. This methodology has proved to be adequate for the detection of unintended stress effects due to the previous treatment with this pesticide. MCR-ALS was performed on augmented matrices built with the LC-MS three-way data obtained from treated and nontreated samples through the sampling time. The strategy allowed us to obtain the concentration and spectra profiles of the main components (previously estimated with the SVD algorithm) from samples treated with pesticide as well as from blank samples, showing how they vary with time after plants treatment with the pesticide. In addition, a simple resolved mass spectrum was obtained corresponding to the peaks of a particular component in all matrices, thus avoiding ambiguity in the compound identity assignment. Different time profiles were found for some metabolites in treated and nontreated samples, which demonstrate that the presence of pesticide causes changes thorough time in the behavior of certain endogenous tomato metabolites as a result of physiological stress

Interactions between milk whey protein and polysaccharide in solution Perez, Adrián Alejandro; Carrara, Carlos Roberto; Carrera Sánchez, Cecilio; Rodríguez Patino, Juan M.; Santiago, Liliana Gabriela In this work we have studied the interactions between a commercial whey protein concentrate (WPC) and two anionic polysaccharides (sodium alginate, SA, and λ-carrageenan, λ-C) in the aqueous phase. The concentration of WPC at 1.0% and the pH 7.0 of the aqueous phase were maintained constant, while polysaccharides (PS) were evaluated within a 0.0–1.0% concentration range. Interactions between WPC and PS in the aqueous phase were analysed by fluorescence spectroscopy, absorption spectroscopy in the presence of methylene blue (MB), and confocal laser scanning microscopy. The results from these methodologies revealed differences in the molecular dynamics of mixed systems. The nature of the interactions between WPC and PS depended on the PS type, its relative concentration in the aqueous phase and also on the two WPC fractions. Whey protein concentrate/sodium alginate (WPC/SA) mixed systems were distinguished by a tendency to protein aggregation in the aqueous phase and their segregation into separated microdomains. On the other hand, WPC/λ-carrageenan (WPC/λ-C) mixed systems showed a high degree of attractive interactions over the whole range of concentrations. The ultrastructure revealed the existence of hybrid macromolecular entities (biopolymer network). Interaction of WPC and polysaccharide in the aqueous phase has an effect on the adsorption of mixed systems at the air–water interface and on their foaming characteristics.

The cytochrome ba complex from the thermoacidophilic crenarchaeote Acidianus ambivalens is an analog of bc1 complexes Bandeiras, Tiago M.; Refojo, Patricia N.; Todorovic, Smilja; Murgida, Daniel Horacio; Hildebrandt, Peter; Bauer, Christian; Pereira, Manuela M.; Kletzin, Arnulf; Teixeira, Miguel A novel cytochrome ba complex was isolated from aerobically grown cells of the thermoacidophilic archaeon Acidianus ambivalens. The complex was purified with two subunits, which are encoded by the cbsA and soxN genes. These genes are part of the pentacistronic cbsAB-soxLN-odsN locus. The spectroscopic characterization revealed the presence of three low-spin hemes, two of the b and one of the as-type with reduction potentials of + 200, + 400 and + 160 mV, respectively. The SoxN protein is proposed to harbor the heme b of lower reduction potential and the heme as, and CbsA the other heme b. The soxL gene encodes a Rieske protein, which was expressed in E. coli; its reduction potential was determined to be + 320 mV. Topology predictions showed that SoxN, CbsB and CbsA should contain 12, 9 and one transmembrane α-helices, respectively, with SoxN having a predicted fold very similar to those of the cytochromes b in bc1 complexes. The presence of two quinol binding motifs was also predicted in SoxN. Based on these findings, we propose that the A. ambivalens cytochrome ba complex is analogous to the bc1 complexes of bacteria and mitochondria, however with distinct subunits and heme types.

pH-dependent mechanism of nitric oxide release in nitrophorins 2 and 4 Swails, Jason M.; Meng, Yilin; Walker, F. Ann; Marti, Marcelo Adrian; Estrin, Dario Ariel; Roitberg, Adrián Nitrophorins are NO carrier proteins that transport and release NO through a pH-dependent conformational change. They bind NO tightly in a low pH environment and release it in a higher pH environment. Experimental evidence shows that the increase in the NO dissociation equilibrium constant, K d, is due mainly to an increase in the NO release rate. Structural and kinetic data strongly suggest that NPs control NO escape by modulating its migration from the active site to the solvent through a pH-dependent conformational change. NP2 and NP4 are two representative proteins of the family displaying a 39% overall sequence identity, and interestingly, NP2 releases NO slower than NP4. The proposal that NPs' NO release relies mainly on the NO escape rate makes NPs a very peculiar case among typical heme proteins. The connection between the pH-dependent conformational change and ligand release mechanism is not fully understood and the structural basis for the pH induced structural transition and the different NO release patterns in NPs are unresolved, yet interesting issues. In this work, we have used state of the art molecular dynamics simulations to study the NO escape process in NP2 and NP4 in both the low and high pH states. Our results show that both NPs modulate NO release by switching between a "closed" conformation in a low pH environment and an "open" conformation at higher pH. In both proteins, the change is caused by the differential protonation of a common residue Asp30 in NP4 and Asp29 in NP2, and the NO escape route is conserved. Finally, our results show that, in NP2, the conformational change to the "open" conformation is smaller than that for NP4 which results in a higher barrier for NO release.

SK2 channels are required for function and long-term survival of efferent synapses on mammalian outer hair cells Murthy, Vidya; Maison, Stéphane F.; Taranda, Julian; Haque, Nadeem; Bond, Chris T.; Elgoyhen, Ana Belen; Adelman, John P.; Liberman, M. Charles; Vetter, Douglas E. Cochlear hair cells use SK2 currents to shape responses to cholinergic efferent feedback from the brain. Using SK2-/- mice, we demonstrate that, in addition to their previously defined role in modulating hair cell membrane potentials, SK2 channels are necessary for long-term survival of olivocochlear fibers and synapses. Loss of the SK2 gene also results in loss of electrically driven olivocochlear effects in vivo, and down regulation of ryanodine receptors involved in calcium-induced calcium release, the main inducer of nAChR evoked SK2 activity. Generation of double-null mice lacking both the α10 nAChR gene, loss of which results in hypertrophied olivocochlear terminals, and the SK2 gene, recapitulates the SK2-/- synaptic phenotype and gene expression, and also leads to down regulation of α9 nAChR gene expression. The data suggest a hierarchy of activity necessary to maintain early olivocochlear synapses at their targets, with SK2 serving an epistatic, upstream, role to the nAChRs.

Role of the pre-A motif in nitric oxide scavenging by truncated hemoglobin HbN of Mycobacterium Tuberculosis Lama, Amriti; Pawarta, Sudesh; Bidon Chanal, Axel; Anand, Arvind; Gelpi, José Luis; Arya, Swati; Marti, Marcelo Adrian; Estrin, Dario Ariel; Luque, F. Javier; Dikshit, Kanak Mycobacterium tuberculosis truncated hemoglobin, HbN, is endowed with a potent nitric-oxide dioxygenase activity and has been found to relieve nitrosative stress and enhance in vivo survival of a heterologous host, Salmonella enterica Typhimurium, within the macrophages. These findings implicate involvement of HbN in the defense of M. tuberculosis against nitrosative stress. The protein carries a tunnel system composed of a short and a long tunnel branch that has been proposed to facilitate diatomic ligand migration to the heme and an unusual Pre-A motif at the N terminus, which does not contribute significantly to the structural integrity of the protein, as it protrudes out of the compact globin fold. Strikingly, deletion of Pre-A region from the M. tuberculosis HbN drastically reduces its ability to scavenge nitric oxide (NO), whereas its insertion at the N terminus of Pre-A lacking HbN of Mycobacterium smegmatis improved its nitric-oxide dioxygenase activity. Titration of the oxygenated adduct of HbN and its mutants with NO indicated that the stoichiometric oxidation of protein is severalfold slower when the Pre-A region is deleted in HbN. Molecular dynamics simulations show that the excision of Pre-A motif results in distinct changes in the protein dynamics, which cause the gate of the tunnel long branch to be trapped into a closed conformation, thus impeding migration of diatomic ligands toward the heme active site. The present study, thus, unequivocally demonstrates vital function of Pre-A region in NO scavenging and unravels its unique role by which HbN might attain its efficient NO-detoxification ability.

Flexibility study for an MSF desalination plant Tarifa, Enrique Eduardo; Franco, Samuel; Humana, Demetrio; Mussati, Sergio Fabian This work addresses a flexibility study on a multi-stage flash (MSF) desalination plant. When any plant is designed, the engineers define the design for reaching optimal operation under nominal conditions. However, uncertain variables or disturbance cannot be handled to obtain those nominal conditions. For this reason, the design contains control elements for compensating the disturbance effects. This compensation is only possible into a region defined by the characteristics of the process and the control elements. When the actual conditions are out of that region, the compensation is not enough, and the plant is not operable. A flexibility study determines the region into which the process is operable. This information can be useful for determining design modifications to improve the process flexibility. A flexibility study involves a complex mathematical model, which is even more complex for a MSF plant. To perform the task, in this work, a stationary simulator was developed for a real-world case study, and the region exploration was performed by Monte Carlo simulation. Results show, in terms of both robustness and speed of computation, that this approach can be a useful tool.

Features of spin-charge separation in the equilibrium conductance through finite rings Jimenez Rincon, Jose Julian; Aligia, Armando Ángel; Hallberg, Karen Astrid We calculate the conductance through rings with few sites L described by the t-J model, threaded by a magnetic flux Φ and weakly coupled to conducting leads at two arbitrary sites. The model can describe a circular array of quantum dots with large charging energy U in comparison with the nearest-neighbor hopping t. We determine analytically the particular values of Φ for which a depression of the transmittance is expected as a consequence of spin-charge separation. We show numerically that the equilibrium conductance at zero temperature is depressed at those particular values of Φ for most systems, in particular at half filling, which might be easier to realize experimentally.

Estructura de la vegetación y selección de hábitats reproductivos en aves del pastizal pampeano; Vegetation structure and selection of reproductive habitats by Pampas grassland birds Cozzani, Natalia Carolina; Zalba, Sergio Martín La transformación acelerada de los pastizales naturales en tierras destinadas a actividades agrícolas y ganaderas afecta de manera particular a las aves de pastizal, cuya reproducción depende de forma estricta de estos ambientes. En este trabajo estudiamos las especies de aves que anidan en el Parque Provincial Ernesto Tornquist, ubicado al sudoeste de la provincia de Buenos Aires. Durante tres temporadas reproductivas realizamos búsquedas intensivas de nidos, registramos las características de los sitios donde estaban construidos y evaluamos las preferencias de las distintas especies por sectores de pajonales cerrados (dominados por Paspalum quadrifarium y Cortaderia selloana) o por áreas de flechillar (pastizales dominados por especies de Stipa y Piptochaetium). Hallamos 214 nidos construidos en matas de pasto o en el suelo, correspondientes a 12 especies. El 76.65% de los nidos se hallaban en sectores de pajonal, pese a que los pajonales representaban solo el 7.75% del área de trabajo, lo cual refleja una preferencia significativa por estos ambientes. Resultó llamativa la abundancia reducida de nidos de especies como Ammodramus humeralis, Cistothorus platensis y Anthus correndera y la ausencia total de otras, como la perdiz colorada (Rhynchotus rufescens), todas ellas aves obligadas de pastizal, asociadas fundamentalmente a ambientes de flechillar. Nuestros resultados podrían reflejar una vulnerabilidad particular de las aves que anidan en los flechillares, los ambientes más afectados en su estructura por el efecto del pastoreo de grandes herbívoros.; Vegetation structure and selection of reproductive habitats by Pampas grassland birds: The increasing transformation of natural grasslands into agricultural fields affects grassland birds with particular severity, as their breeding success depends strictly on these habitats. This study focuses on bird species that nest in the Ernesto Tornquist Provincial Park in the southwest of Buenos Aires province (Argentina). We conducted intensive nest surveys during three reproductive seasons, recording their site characteristics and evaluating nesting preferences of needlegrass grasslands (dominated by Stipa and Piptochaetium species, "flechillares") and tussock grasslands (dominated by Paspalum quadrifarium and Cortaderia selloana). We found 214 nests, belonging to 12 species, built within grass tussocks or directly on the ground. Paspalum grasslands represent 7.75% of the surveyed area but contained 76.65% of the nests, showing a significant preference for this type of habitat. Low nest abundance of obligate grassland species, typically associated to "flechillares", e.g. Grassland Sparrow (Ammodramus humeralis), Grass Wren (Cistothorus platensis) and Correndera Pipit (Anthus correndera), and the complete absence of Red-winged Tinamou (Rhynchotus rufescens) nests, was particularly worrying. Our results may reflect the particular vulnerability of species nesting in "flechillares", a habitat the structure of which is more deeply affected by big herbivores.